/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.activiti.engine.impl.bpmn.helper;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;

import org.activiti.engine.ActivitiException;
import org.activiti.engine.ActivitiIllegalArgumentException;
import org.activiti.engine.delegate.BpmnError;
import org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior;
import org.activiti.engine.impl.bpmn.behavior.ServiceTaskJavaDelegateActivityBehavior;
import org.activiti.engine.impl.bpmn.parser.FieldDeclaration;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.delegate.ExecutionListenerInvocation;
import org.activiti.engine.impl.delegate.TaskListenerInvocation;
import org.activiti.engine.impl.pvm.delegate.ActivityExecution;
import org.activiti.engine.impl.pvm.delegate.SignallableActivityBehavior;
import org.activiti.engine.impl.pvm.delegate.SubProcessActivityBehavior;
import org.activiti.engine.impl.util.ReflectUtil;
import org.apache.commons.lang3.StringUtils;
import org.flowable.bpmn.model.MapExceptionEntry;
import org.flowable.common.engine.api.delegate.Expression;
import org.flowable.engine.DynamicBpmnConstants;
import org.flowable.engine.delegate.DelegateExecution;
import org.flowable.engine.delegate.ExecutionListener;
import org.flowable.engine.delegate.JavaDelegate;
import org.flowable.engine.delegate.TaskListener;
import org.flowable.engine.impl.delegate.ActivityBehavior;
import org.flowable.task.service.delegate.DelegateTask;

import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * Helper class for bpmn constructs that allow class delegation.
 *
 * This class will lazily instantiate the referenced classes when needed at runtime.
 * 
 * @author Joram Barrez
 * @author Falko Menge
 * @author Saeid Mirzaei
 */
public class ClassDelegate extends AbstractBpmnActivityBehavior implements TaskListener, ExecutionListener, SubProcessActivityBehavior {

    protected String className;
    protected List<FieldDeclaration> fieldDeclarations;
    protected ExecutionListener executionListenerInstance;
    protected TaskListener taskListenerInstance;
    protected ActivityBehavior activityBehaviorInstance;
    protected Expression skipExpression;
    protected List<MapExceptionEntry> mapExceptions;
    protected String serviceTaskId;

    public ClassDelegate(String className, List<FieldDeclaration> fieldDeclarations, Expression skipExpression) {
        this.className = className;
        this.fieldDeclarations = fieldDeclarations;
        this.skipExpression = skipExpression;

    }

    public ClassDelegate(String id, String className, List<FieldDeclaration> fieldDeclarations, Expression skipExpression, List<MapExceptionEntry> mapExceptions) {
        this(className, fieldDeclarations, skipExpression);
        this.serviceTaskId = id;
        this.mapExceptions = mapExceptions;
    }

    public ClassDelegate(String className, List<FieldDeclaration> fieldDeclarations) {
        this(className, fieldDeclarations, null);
    }

    public ClassDelegate(Class<?> clazz, List<FieldDeclaration> fieldDeclarations) {
        this(clazz.getName(), fieldDeclarations, null);
    }

    public ClassDelegate(Class<?> clazz, List<FieldDeclaration> fieldDeclarations, Expression skipExpression) {
        this(clazz.getName(), fieldDeclarations, skipExpression);
    }

    // Execution listener
    @Override
    public void notify(DelegateExecution execution) {
        if (executionListenerInstance == null) {
            executionListenerInstance = getExecutionListenerInstance();
        }
        Context.getProcessEngineConfiguration()
                .getDelegateInterceptor()
                .handleInvocation(new ExecutionListenerInvocation(executionListenerInstance, execution));
    }

    protected ExecutionListener getExecutionListenerInstance() {
        Object delegateInstance = instantiateDelegate(className, fieldDeclarations);
        if (delegateInstance instanceof ExecutionListener) {
            return (ExecutionListener) delegateInstance;
        } else if (delegateInstance instanceof JavaDelegate) {
            return new ServiceTaskJavaDelegateActivityBehavior((JavaDelegate) delegateInstance, skipExpression);
        } else {
            throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + ExecutionListener.class + " nor " + JavaDelegate.class);
        }
    }

    // Task listener
    @Override
    public void notify(DelegateTask delegateTask) {
        if (taskListenerInstance == null) {
            taskListenerInstance = getTaskListenerInstance();
        }
        try {
            Context.getProcessEngineConfiguration()
                    .getDelegateInterceptor()
                    .handleInvocation(new TaskListenerInvocation(taskListenerInstance, delegateTask));
        } catch (Exception e) {
            throw new ActivitiException("Exception while invoking TaskListener: " + e.getMessage(), e);
        }
    }

    protected TaskListener getTaskListenerInstance() {
        Object delegateInstance = instantiateDelegate(className, fieldDeclarations);
        if (delegateInstance instanceof TaskListener) {
            return (TaskListener) delegateInstance;
        } else {
            throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + TaskListener.class);
        }
    }

    // Activity Behavior
    @Override
    public void execute(DelegateExecution execution) {
        ActivityExecution activityExecution = (ActivityExecution) execution;

        if (Context.getProcessEngineConfiguration().isEnableProcessDefinitionInfoCache()) {
            ObjectNode taskElementProperties = Context.getBpmnOverrideElementProperties(serviceTaskId, execution.getProcessDefinitionId());
            if (taskElementProperties != null && taskElementProperties.has(DynamicBpmnConstants.SERVICE_TASK_CLASS_NAME)) {
                String overrideClassName = taskElementProperties.get(DynamicBpmnConstants.SERVICE_TASK_CLASS_NAME).asText();
                if (StringUtils.isNotEmpty(overrideClassName) && !overrideClassName.equals(className)) {
                    className = overrideClassName;
                    activityBehaviorInstance = null;
                }
            }
        }

        if (activityBehaviorInstance == null) {
            activityBehaviorInstance = getActivityBehaviorInstance(activityExecution);
        }

        try {
            activityBehaviorInstance.execute(execution);
        } catch (BpmnError error) {
            ErrorPropagation.propagateError(error, activityExecution);
        } catch (RuntimeException e) {
            if (!ErrorPropagation.mapException(e, activityExecution, mapExceptions))
                throw e;
        }
    }

    // Signallable activity behavior
    @Override
    public void signal(ActivityExecution execution, String signalName, Object signalData) throws Exception {
        if (activityBehaviorInstance == null) {
            activityBehaviorInstance = getActivityBehaviorInstance(execution);
        }

        if (activityBehaviorInstance instanceof SignallableActivityBehavior) {
            ((SignallableActivityBehavior) activityBehaviorInstance).signal(execution, signalName, signalData);
        } else {
            throw new ActivitiException("signal() can only be called on a " + SignallableActivityBehavior.class.getName() + " instance");
        }
    }

    // Subprocess activityBehaviour

    @Override
    public void completing(DelegateExecution execution, DelegateExecution subProcessInstance) throws Exception {
        if (activityBehaviorInstance == null) {
            activityBehaviorInstance = getActivityBehaviorInstance((ActivityExecution) execution);
        }

        if (activityBehaviorInstance instanceof SubProcessActivityBehavior) {
            ((SubProcessActivityBehavior) activityBehaviorInstance).completing(execution, subProcessInstance);
        } else {
            throw new ActivitiException("completing() can only be called on a " + SubProcessActivityBehavior.class.getName() + " instance");
        }
    }

    @Override
    public void completed(ActivityExecution execution) throws Exception {
        if (activityBehaviorInstance == null) {
            activityBehaviorInstance = getActivityBehaviorInstance(execution);
        }

        if (activityBehaviorInstance instanceof SubProcessActivityBehavior) {
            ((SubProcessActivityBehavior) activityBehaviorInstance).completed(execution);
        } else {
            throw new ActivitiException("completed() can only be called on a " + SubProcessActivityBehavior.class.getName() + " instance");
        }
    }

    protected ActivityBehavior getActivityBehaviorInstance(ActivityExecution execution) {
        Object delegateInstance = instantiateDelegate(className, fieldDeclarations);

        if (delegateInstance instanceof ActivityBehavior) {
            return determineBehaviour((ActivityBehavior) delegateInstance, execution);
        } else if (delegateInstance instanceof JavaDelegate) {
            return determineBehaviour(new ServiceTaskJavaDelegateActivityBehavior((JavaDelegate) delegateInstance, skipExpression), execution);
        } else {
            throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + JavaDelegate.class.getName() + " nor " + ActivityBehavior.class.getName());
        }
    }

    // Adds properties to the given delegation instance (eg multi instance) if needed
    protected ActivityBehavior determineBehaviour(ActivityBehavior delegateInstance, ActivityExecution execution) {
        if (hasMultiInstanceCharacteristics()) {
            multiInstanceActivityBehavior.setInnerActivityBehavior((AbstractBpmnActivityBehavior) delegateInstance);
            return multiInstanceActivityBehavior;
        }
        return delegateInstance;
    }

    protected Object instantiateDelegate(String className, List<FieldDeclaration> fieldDeclarations) {
        return ClassDelegate.defaultInstantiateDelegate(className, fieldDeclarations);
    }

    // --HELPER METHODS (also usable by external classes) ----------------------------------------

    public static Object defaultInstantiateDelegate(Class<?> clazz, List<FieldDeclaration> fieldDeclarations) {
        return defaultInstantiateDelegate(clazz.getName(), fieldDeclarations);
    }

    public static Object defaultInstantiateDelegate(String className, List<FieldDeclaration> fieldDeclarations) {
        Object object = ReflectUtil.instantiate(className);
        applyFieldDeclaration(fieldDeclarations, object);
        return object;
    }

    public static void applyFieldDeclaration(List<FieldDeclaration> fieldDeclarations, Object target) {
        applyFieldDeclaration(fieldDeclarations, target, true);
    }

    public static void applyFieldDeclaration(List<FieldDeclaration> fieldDeclarations, Object target, boolean throwExceptionOnMissingField) {
        if (fieldDeclarations != null) {
            for (FieldDeclaration declaration : fieldDeclarations) {
                applyFieldDeclaration(declaration, target, throwExceptionOnMissingField);
            }
        }
    }

    public static void applyFieldDeclaration(FieldDeclaration declaration, Object target) {
        applyFieldDeclaration(declaration, target, true);
    }

    public static void applyFieldDeclaration(FieldDeclaration declaration, Object target, boolean throwExceptionOnMissingField) {
        Method setterMethod = ReflectUtil.getSetter(declaration.getName(),
                target.getClass(), declaration.getValue().getClass());

        if (setterMethod != null) {
            try {
                setterMethod.invoke(target, declaration.getValue());
            } catch (IllegalArgumentException e) {
                throw new ActivitiException("Error while invoking '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
            } catch (IllegalAccessException e) {
                throw new ActivitiException("Illegal access when calling '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
            } catch (InvocationTargetException e) {
                throw new ActivitiException("Exception while invoking '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
            }
        } else {
            Field field = ReflectUtil.getField(declaration.getName(), target);
            if (field == null) {
                if (throwExceptionOnMissingField) {
                    throw new ActivitiIllegalArgumentException("Field definition uses unexisting field '" + declaration.getName() + "' on class " + target.getClass().getName());
                } else {
                    return;
                }
            }

            // Check if the delegate field's type is correct
            if (!fieldTypeCompatible(declaration, field)) {
                throw new ActivitiIllegalArgumentException("Incompatible type set on field declaration '" + declaration.getName()
                        + "' for class " + target.getClass().getName()
                        + ". Declared value has type " + declaration.getValue().getClass().getName()
                        + ", while expecting " + field.getType().getName());
            }
            ReflectUtil.setField(field, target, declaration.getValue());

        }
    }

    public static boolean fieldTypeCompatible(FieldDeclaration declaration, Field field) {
        if (declaration.getValue() != null) {
            return field.getType().isAssignableFrom(declaration.getValue().getClass());
        } else {
            // Null can be set any field type
            return true;
        }
    }

    /**
     * returns the class name this {@link ClassDelegate} is configured to. Comes in handy if you want to check which delegates you already have e.g. in a list of listeners
     */
    public String getClassName() {
        return className;
    }

}
